1. Technical Field
The present invention relates to a photoelectric conversion device that converts light energy into electrical energy, and the electronic apparatus including the photoelectric conversion device.
2. Related Art
A solar cell including a light absorption layer is a typical example of photoelectric conversion devices. The light absorption layer may be made of a CIS thin film, such as a CuInSe2 or CuInGaSe film, which is an p-type semiconductor film having a chalcopyrite structure. CIS thin films have high photosensitivity to light over a wide range of wavelengths from visible light to near-infrared light, and are accordingly expected to be used in photodetectors. On the other hand, CIS thin films are liable to be damaged when being formed for a photodetector, and the damaged CIS film undesirably causes leakage of current.
International Publication No. 2008/093834 discloses a method for manufacturing a solid state image pickup device that includes patterning a compound semiconductor film (CIS thin film) formed on a lower electrode layer by photolithography so as to be divided with the lower electrode layer for each pixel, forming a buffer layer so as to cover the compound semiconductor film, and forming an optically transparent electrode layer on the buffer layer.
In this method, the buffer layer is formed between the compound semiconductor film and the optically transparent electrode layer. The buffer layer alleviates the damage to the compound semiconductor film that may occur when the optically transparent electrode layer is formed, and thus can reduce leakage of current resulting from the damage.
JP-A-2007-123720 discloses a photoelectric conversion device including an optically transparent electrode layer that is disposed in such a manner that the ends of the compound semiconductor film are located on the outside of the ends of the optically transparent electrode layer. According to this disclosure, since the ends of the compound semiconductor film are located on the outside of the ends of the optically transparent electrode layer, leakage of current can be reduced even if the compound semiconductor film is damaged at an end thereof or has a crystal defect therein by an operation for patterning the compound semiconductor film.
While the solid state image pickup device produced by the method disclosed in International Publication No. 2008/093834 is effective in reducing leakage of current that may occur when a forward bias is applied, however, it is difficult to reduce leakage of current (dark current) that may occur when a reverse bias is applied.
In either disclosure of International Publication No. 2008/093834 or JP-A-2007-123720, a crystalline CdS buffer layer is formed between a compound semiconductor film and an optically transparent electrode layer by a solution growth method that can form a film having high coating power. However, if the CdS film has a crystal defect, leakage of current occurs undesirably at the position of the crystal defect.